1. Field of the Invention
The present invention relates in general to mechanical robotic grippers. More particularly, the present invention relates to appendages for use in robotics applications and to apparatus and methods for improved grasping by robotic fingers.
2. The Prior Art
The mechanical robotic grippers of an industrial robot often utilize “fingers” assembled from links and joints as the primary grasping mechanism of the manipulator. When a robotic gripper grasps an object, it places its fingers onto the object with the intent to secure a good grasp. A challenge in robotic grasping systems is to obtain a good grasp on an object so that it is stable and does not slip while being grasped.
One aspect of the challenge for achieving a good grasp is the high computational complexity involved in identifying how to grasp an object. Placing the “fingers” onto the object in the correct locations to achieve good stability requires computing the positions of multiple joints of the robotic gripper so that there is an adequate surface contact and complementary forces to achieve a stable grasp.
Another challenge in achieving a good grasp is the mechanical complexity of having many independently motorized joints. This increases weight, cost and reliability challenges in the robotic grippers.
A class of robotic grippers has been previously implemented that provide a significant reduction in both the computational complexity and mechanical complexity of robotic grippers while still achieving a good grasp on objects. This class of robotic grippers is known as under-actuated robotic grippers. The key attribute of under-actuated robotic grippers is that multiple joints of the robotic gripper are dependent on a single actuator and provides a finger wrapping action onto objects to achieve high quality grasps. This operating modality requires less computational processing to define the grasp as compared to fully articulated robotic grippers.
Another challenge with robotic grippers is providing a grasp configuration that can allow multiple fingers to grasp objects having different sizes and shapes. A simple example is a robotic gripper that needs to pick up both a large ball, such as a softball and a small ball such as a golf ball or ping-pong ball or another relatively small object. To optimally grasp each of these objects, the fingers of the robotic gripper will need a wider placement for the large ball and a narrower placement for the small ball. Robotic grippers have been developed that are able to adjust their finger spacing to accommodate these types of differences, but with a trade-off in increased weight, complexity, and cost, as well as reduced reliability.